Tube-protected contact-making device



Jan. 12, 1960 F. PFLEIDERER TUBE-PROTECTED CONTACT-MAKING DEVICE Filed July 18, 1958 Fig.2

Fig. 3

United States Patent 2,921,163 TUBE-PROTECTED CONTACT-MAKING DEVICE Friedrich Pfleiderer, Munich-Solln, Germany, assignor to Siemens and Halske Aktiengesellschaft, Berlin and Munich, Germany, a corporation of Germany Application July 18, 1958, Serial No. 749,507 v Claims priority, application Germany August 13, 1957 4 Claims. (Cl. 200-87) This invention is concerned with a sealed-in or tubeprotected contact-making device. The object of the invention is to provide a tube-protected contact-making device comprising means built into the contact springs for holding such springs in operatively actuated closed position depending upon the current flowing therethrough, thereby eliminating the necessity for separate holding means such as holding coils or switches or permanent magnets and the like.

Sealed-in contacts are in known manner actuated by impressing upon the contact springs thereof a magnetic flux which generates across the working air gap a field causing attraction of the contact springs and therewith closure of the contact points. The magnetic flux is customarily produced by means of an energizing or exciter winding or coil surrounding the sealed-in contact.

In case a sealed-in contact is to be held in operatively actuated, that is, in closed position, a holding fiux must be generated to flow over the contact springs after closure thereof. Such holding flux may be generated either by the exciter winding or by a separate holding winding. It has also been proposed to provide a permanent magnet for producing the holding flux.

The invention shows a way of eliminating separate windings or permanent magnets and the like, for generating the holding flux, resulting in considerable reduction of expenditure required for circuits employing sealed-in contacts.

In accordance with the invention, the contact springs are provided centrally thereof with contact portions having an electrical conductivity which is substantially higher than that of adjacent portions of the springs, causing in the presence of current flow across the closed contact portions generation of a magnetic field surrounding the corresponding portion annularly, such field permeating both contact springs and holding such springs in closed position.

The holding of the contact springs in the sealed-in contact device according to the invention, in closed position thereof, may thus be made to depend upon the current flowing over the contact springs, that is, the contacts will remain closed so long as current flow is maintained thereover in the circuit in which the corresponding contacts are included.

The various objects and features of the invention will appear from the description which will be rendered below with reference to the accompanying diagrammatic drawing, in which Fig. 1 shows on an enlarged scale a known sealed-in contact device;

Fig. 2 is a greatly enlarged perspective view of an example of the invention, showing contact springs compris' ing contact portions of high conductivity; and

Fig. 3 is a sectional view of the contact springs in closed position thereof.

The known sealed-in contact shown in Fig. 1 comprises contact springs F1 and F2 extending in sealed relation into the vessel or tube S. The tube is surrounded by an 2,921,163 Patented Jan. 12, 1960 ice lapping relationship. Letter D indicates a terminal wire connected to the contact spring F1. Electrical conductors L1 and L2 are respectively embedded centrally of the contact springs F1 and F2 along the facing sides of the springs. The conductivity of these conductors is considerably higher than that of the surrounding spring material. The corresponding conductors may, for example, be made of silver which has a higher conductivity as compared with usual spring material, for example, iron. The contact springs F1 and F2 may be included in a circuit to be controlled thereby and may be contained within a vessel such as S (Fig. l) which is surrounded by an energizing or exciting winding or coil-such as W. Accordingly, energization of the winding W will produce a magnetic flux across the air gap separating the contact springs in normal position thereof, producing a mutual attraction between the contact springs and consequently closure thereof, thus causing current to flow thereover in the circuit controlled thereby. The current will however fiow predominantly along the conductors L1 and L2 due to the high conductivity of such conductors.

The result of such current flow may be explained with reference to Fig. 3 showing on a greatly enlarged scale a cross sectional view of contact springs made in accordance with the invention, in closed position thereof. The conductors L1 and L2 are disposed centrally of the contact-making areas or portions of the contact springs F1 and F2, resulting in a current concentration along the conductors L1 and L2. As a consequence of such current concentration centrally of the closed contact springs, there will be produced a magnetic field as indicated in dotted lines, extending annularly about the conductors L1 and L2, such field extending into and effecting both contact springs F1 and F2 and exerting a force of mutual attraction between the contact springs, thereby causing the springs to remain in closed position. A prerequisite for the contact-holding action is that the current flowing along the embedded conductors is of sufiicient value to produce the magnetic holding field.

Maximum current concentration along the embedded conductors L1 and L2 will be obtained by electrically insulating them with respect to the surrounding flux-carrying spring material and maintaining electrical connection thereof with the terminals of the device. As shown in Fig. 2, such connection is maintained by extending the conductor L1 embedded in the spring F1 to the terminal D and electrically connecting it with such terminal. The insulation of the embedded conductors with respect to the adjacent spring material may be effected in known and suitable manner, for example, by means of an oxide layer.

Care must be taken upon embedding the conductors L1 and L2 respectively in the contact springs F1 and F2, to position them so that contact engagement will be reliably obtained responsive to operative actuation of the corresponding contact springs. If desired, the plane surfaces of the conductors may for this purpose extend slightly beyond the corresponding planes of the contact springs, resulting in actuated position in an air gap between the fiux-carrying portions of the contact spring which, however, must be of practically negligible value to avoid weakening the magnetic flux extending annularly into and normally positioned therein separated by a gap,

each contact spring carrying upon the side thereof which faces the other contact spring a contact portion extending centrally of said side longitudinally of the corresponding contact spring made of a material having an electrical conductivity exceeding that of the spring material disposed adjacent thereto, means for generating a magnetic flux to eifect mutual attraction between said contact springs so as to eifect contact-making engagement between said contact portions, current flowing through the engaged contact portions generating a magnetic field extending .within and through said contact springs annularly about said contact portions, said magnetic field being about the conductorsin closed position of the contact effective to hold said contact portions in contact-making engagement for the duration of current flow through said springs. g t

2. A contact-making device according to claim 1, wherein the contact portion on each of said contact springs is an electrical conductor embedded therein, the higher conductivity of said contact portions causing upon contact-making engagement thereof current concentration therein for producing said magnetic holding field.

3 A contact-making device according to claim 2, wherein said contact portionsare interconnectedwith the terminals extending from the respective contact springs.

4. A' contact-making device according to claim 3, wherein {said contact portions are insulated from the material of the corresponding contact springs.

References Cited in the file of this patent UNITED STATES PATENTS 

